In a slewing apparatus that slews with a suspended load suspended from the tip of a boom, a technology of suppressing swing of the suspended load after the slewing has been known. For example, Patent Literature (hereinafter, abbreviated as PTL) 1 discloses that swing of a suspended load is suppressed by setting an acceleration interval and a deceleration interval of slewing to a time that is an integral multiple of the swing cycle of a suspended load that is in a pendulum motion. PTL 2 discloses that swing of a suspended load is suppressed by allowing each of an acceleration interval and a deceleration interval to include a constant velocity interval.